Roofer&#39;s kneepads

ABSTRACT

The invention is a wedge-shaped support adapted to be fastened to a user&#39;s lower leg to provide comfort when the user is kneeling on an inclined roof, used in pairs. Each shin wedge comprises a wedge of lightweight material capable of supporting the user&#39;s weight. The acute dihedral angle of each wedge is approximately equal to the pitch angle of the roof on which the wedge kneepads are being used, thereby providing a substantially horizontal upper kneeling surface when the wedge is oriented towards the peak of the roof. The wedge&#39;s lower surface typically comprises a durable pad that prevents premature abrasion of the lightweight material and improves grip onto the inclined surface. Each wedge&#39;s upper surface typically includes a soft layer that serves as an ergonomic kneeling pad for the user. An attachment harness secures the wedge kneepad to the user&#39;s shin and thigh or knee.

FIELD OF THE INVENTION

The invention relates to kneepads and shin pads and means foralleviating pressure and discomfort of the knees and legs of workerswhen they are working on inclined surfaces such as roofs.

BACKGROUND TO THE INVENTION

Kneeling to work on either a sloped surface such as a roof, or ahorizontal surface such as a floor, presents an ergonomicallychallenging task that stresses a worker's legs and feet. When a workeris kneeling on any surface, either with both knees or partially kneelingon one knee, the front of the worker's knee makes contact and supportsthe bulk of the worker's weight. Contact with the surface is made,through the skin of course, by the upper part of the shin bone, alsocalled the tibia, and sometimes but not necessarily the kneecap, alsocalled the patella. This contact surface has no established name, andwill here be called the “kneefront”. However the worker's toes musttypically apply balancing pressure that varies with upper body posture.Each of the worker's legs forms an open triangle over the work surfacecomprised of the kneefront and unsupported along the triangle's topside, the foot and toe oriented roughly at a right angle to the shin andforming its second side, with the floor or roof or other kneelingsurface closing the triangle along its bottom side between the toe andkneefront. This unsupported leg geometry continuously strains a kneelingworker's ankle and toe muscles as they counterbalance fore and aftmotions of the upper body, regardless of whether a task is beingperformed on a flat or inclined surface. It also puts strain on theworker's back.

These kneeling strains are considerably exacerbated when working on aninclined surface such as a roof because gravity imposes a relentlessshear force onto all points where the worker contacts the slopedsurface. The shear force results in an unpleasant feeling, as theworker's skin, whether through clothing or not, stretches to stopsliding down the roof. The worker's ankles and toes also experienceincreased stress due to force exerted by the body's weight tending tomove down the slope, which the feet must be continuously counteracting,regardless of upper body posture. The strain on the back is also worsein this position.

A wide variety of kneepads exists in the prior art. They could generallybe classed as simple “kneefront protectors”. In general, the prior artkneepads do not alleviate the foot muscle strain caused by unsupportedshins, and none provide relief from the shear forces experienced whenworking on an inclined work surface.

A few more advanced kneepads attempt to exploit the users shin, definedas the front part of the leg below the knee and above the ankle, inorder to spread the kneeling forces onto a larger area and therebyimprove comfort. U.S. Pat. No. 6,795,974 to Howell discloses a kneepadthat extends over the shin, but does not have any significant thicknessto raise the feet partly or fully off the kneeling surface. U.S. Pat.No. 6,637,034 to Worden discloses a kneepad that extends along the shinand raises the knee from the kneeling surface, but leaves the foot asthe other point of support, so that the main result is that the knee isless bent than it would be without that kneepad.

U.S. Pat. No. 4,438,754 to Canney discloses a knee protector that doesnot make contact with the kneefront, but straps to the shin and leavesthe kneefront in mid-air. This creates an uncomfortable, or uneasyfeeling in the wearer, and undue pressure on the knee joint becausethere is no support directly under the thigh which is putting downwardpressure on the knee joint.

U.S. Pat. No. 6,845,515 to Sveilich discloses a shin rest that isrelatively short, at about 5 to 10 inches, and is intended to be wornlow on the leg and used in association with a separate kneepad. Sveilichdiscloses one embodiment that joins the kneepad to the shin rest, at anarticulated joint, which would be altogether quite long and massive andthat is undesirable for the wearer when standing up while still wearingthe device.

All of these kneepads and shin rests in the prior art have essentiallyconstant thickness, and are best suited for working on a horizontalsurface. The present invention is intended for working on a slopedsurface, such as a roof. The present invention comprises a wedge shapethat is not found in the prior art.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the deficienciesnoted in the prior art concerning kneepads, particularly as they pertainto working on an inclined roof. It is another object of the presentinvention to provide kneepads that reduce or eliminate pressure on itsuser's feet.

It is another object of the present invention to provide shin wedgesthat reduce or eliminate shear forces on a user's body when working onan inclined surface.

It is another object of the present invention to increase the safety ofworkers on steeply inclined surfaces by increasing their frictionalcontact onto it.

These objects are attained by a shin wedge comprising a body that iswedge shaped, having an upper surface that is dimensioned and configuredto support a user's kneefront and to supportingly hold a portion of auser's shin, and having a lower surface that comprises a substantialarea that is substantially flat. The upper surface extends from a user'skneefront distally to more than one-quarter of the distance along theuser's shin but less than one-half of the distance along the user'sshin. There is a third surface that faces in the direction of a user'sfoot. One or more harness straps are connected to that body, and aredimensioned and configured to secure the shin wedge to a user's leg.

The dihedral angle included between the upper surface and the lowersurface is called here the “wedge angle”.

The user of the present invention is more comfortable because the effectof the incline is substantially eliminated, and the user feels as if heis kneeling on a nearly horizontal surface. This reduces strain on theback, ankle, and toes. The shearing force on the skin of the user,whether felt through clothing or directly on the skin, is completelyeliminated if the wedge angle is the same as the pitch of the roof. Moregenerally, that shearing force is at least substantially reduced inproportion to how closely the wedge angle equals the pitch of the roof.

Furthermore, the user is safer because the contact with the roof is theentire bottom surface of the shin wedge, which can easily be made muchlarger than the combined area of a person's kneefronts and toes, even ifthe kneefront is supplemented by the sort of kneepad existing in theprior art.

The force of gravity is vertical and in the customary notation ofphysics is m*g, where m is the mass (in this case, of the worker plusthe shin wedge) and g is the acceleration of gravity. When the mass isresting on an inclined plane (such as a roof) having pitch angle P,measured from horizontal, the force of gravity can be resolved intom*g*sin(P) pointing along the roof, and m*g*cos(P) perpendicular to theroof. The vector m*g*cos(P) is not relevant to the following discussion.It is the force vector m*g*sin(P) that causes the worker to slide downthe roof. The frictional force that resists sliding of the shin wedge isa vector pointing along the roof in the opposite direction tom*g*sin(P). Undesired sliding occurs when the force vector m*g*sin(P)exceeds the frictional force. As the value of P increases, sin(P)increases, and more frictional force is needed. The wedge angle does notcome into this calculation directly. The only way to increase frictionalforce is to increase the area of the shin wedge in contact with theroof, or to enhance its frictional properties. A larger wedge angle fora given length of the shin wedge along the user's shin will result in alonger surface, that being the hypotenuse of the triangle in which thelength along the shin is adjacent to the wedge angle. Therefore, thewedge angle comes indirectly into the calculations for resistingsliding, by increasing the area providing the friction. The sine forP=45 degrees is approximately twice the sine for P=20 degrees, so thearea of frictional contact, and the frictional force (although that alsodepends on the friction material) would be approximately double for ashin wedge with wedge angle 45 degrees compared to a shin wedge withwedge angle 20 degrees. No knee or shin protector in the prior art hasthis beneficial effect that increases safety of the user of the presentinvention.

These and other objects, features, and characteristics of the presentinvention will be more apparent upon consideration of the followingdetailed description and appended claims with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of the invention will now be described indetail with reference to the following drawings, in which:

FIG. 1 illustrates a shin wedge according to the present invention, inthe environment in which it is used.

FIG. 2 is a large-scale illustration of one of the shin wedges shown inFIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, roofer 1 is shown kneeling comfortably on inclinedroof surface 3 using a pair of shin wedges 2 configured according to thepresent invention. The shape of the shin wedges is generally that of awedge, having two non-parallel plane surfaces meeting at the thin sideof the solid figure but not necessarily forming a sharp edge there. Thisshape could be described as a blunt wedge, but here is simply called“wedge”. The top surface may be not a flat plane, but rather (as will bedescribed below) it may have a lengthwise depression to conform to theshin of the user. Opposite the thin blunt side is a thicker side tocomplete the solid triangle. The shin wedges are always worn so that thethin end is near the users knee (the proximal end) and the thick end istowards the foot (the distal end).

The shin wedge also usefully provides leverage, allowing the user tolever a knee up by rotation of the shin wedge about its distal edge.

In FIG. 1, for illustration, the wedge angle, is the same angle as thepitch of the roof, so that the upper plane is horizontal, and thereforethe user's kneefronts and shins rest on a horizontal surface, which isthe position of least discomfort. In general, the closer the wedge angleis to the pitch of the roof, the greater the comfort of the roofer,because drag on the skin is reduced. However, the wedge angle and thepitch will not be equal in all cases, and any particular shin wedge canbe used on roofs with various pitches. The wedge angle may be greaterthan the pitch of the roof or less than the pitch of the roof,circumstances called here “over-wedging” and “under-wedging”respectively.

In a case of over-wedging, the user's shin will be sloping down towardsthe kneefront, and this is reasonably comfortable as that is the angleof the shin when a person is kneeling on a horizontal surface withoutany support other than the kneefronts and feet. The tendency, althoughsmall, is to slide forward, and that is less distressing and more easilymanaged than a tendency to slide backward.

In a case of under-wedging, the user's shin will be sloping down towardsthe foot, and that resembles the situation of working without anysupport other than the kneefronts and feet on a sloping roof of lesserpitch. The present invention then has the effect of reducing theapparent pitch of the roof, which is beneficial to the comfort andsafety of the roofer. In cases of pitches of approximately 30 degrees ormore, the user should choose a shin wedge with a wedge angle moderatelyclose to the pitch. For steep pitches, usually thought of as 45 degreesor more, the present invention will still be useful, but should not berelied on without other safety measures such as safety ropes.

In FIG. 1, the roofer's kneefronts 4 and at least a portion of theroofer's shins 5 rest upon the shin wedges 2 and are secured in place bymeans of harness straps 6 and 8. The roofer's feet 7 are thereby held atleast partly suspended above the roof. If the toes of the feet or thetoe of the user's boot are touching the roof and the roofer does notwant that, a small turn of the foot sideways, with either the toes goinginward or outward in relation to the body, would lift the toes clear ofthe roof. In this way, the roofer can relieve muscle stresses that wouldnormally be needed to restrain him from sliding down the roof 3. Sincethe upper surface of each shin wedge is approximately horizontal, littleor no shear force is applied to the user's kneefront or shin at anytime. All forces between the anatomy of user 1 and the shin wedges 2 arewidely spread compressive loads onto the shin bone and kneefront, whichis strong and well adapted to bear loads, rather than shearing loadsonto skin of the kneefront, thereby minimizing discomfort.

FIG. 2 shows one of the shin wedges 2 shown in FIG. 1. Each shin wedge 2comprises wedge body 11 having an upper surface 12 for engagement to auser such as a kneeling roofer, a lower surface 13 for engagement to awork surface such as an inclined roof, triangular wedge sides 14 and 15,and rear face 16. The wedge angle 17 between upper and lower surfaces 12and 13 is approximately equal to the pitch of the inclined surface uponwhich the user will kneel.

Wedge body 11 is typically made of a lightweight plastic material suchas a thermoplastic elastomer or expanded polystyrene, thereby providingsufficient strength to support a user while minimizing weight that wouldbe an encumbrance when the user is walking upright while wearing theshin wedges. The width of each wedge body 11 is typically in the range 4to 7 inches, with about 5 inches preferred. Its length is in the range 6to 16 inches, with about 9 inches preferred, and in any case should stopwell above the ankle. The longer it would be, the heavier it would be,and since it begins at the kneefront, it typically extends fromone-third to one-half of the distance from the kneefront to the ankle.That length gives sufficient support to the shin, and a longersupporting surface is not a good trade-off for the added weight andbulk. Lengths in the stated range give sufficient leverage. That rangeof width and length gives sufficient contact area with an inclinedsurface so that a useful coefficient of friction may be obtained withsuitable material on the lower surface 13. The coefficient of frictionbetween two surfaces depends on the nature of both surfaces. The roofson which this may be used may be of a variety of materials, includingasphalt shingles, wood, copper, steel, tile, slate, and waterproofingmembrane. The metal roofs contribute little to the friction, so thematerial on the lower surface 13 must accommodate that fact.

The height of its rear face 16, which faces the foot, varies with theangle 17 used to compensate for roof pitch. The angle from a typicaluser's kneefront to the toe of a boot is in the range 15 degrees to 20degrees. For such a user, if the wedge angle is greater than that angle,a toe will not make contact with the roof. That is not the preferredsituation, but individual users will decide for themselves on whetherthey will tolerate that situation, or tolerate significantunder-wedging. A small wedge angle of about 10 degrees might bepreferred by some users.

The dimensions stated here are rough approximations and may vary as thegeneral wedge shape is rounded or sculpted for either ergonomic orstylistic reasons. Rounded edges 25, 26 and 27 at the lower surface 13allow the user easier movement when crawling in any direction on theroof, because relatively sharp edges would tend to catch on the roof.

Each shin wedge 2 includes an attachment harness comprising one or moreadjustable straps 6, each configured for securing the user's shinagainst the upper surface 12 of the shin wedge 2. Optionally, there maybe a harness element 8 that can encircle the user's leg at or above theknee, which would be attached to the front of the wedge body 11 by agarter strap 18.

Adjustable straps 6 and 8 may be somewhat elastic to aid in achieving asecure fit. Various well-known length adjustment and strap positioningfixtures may be supplied to insure proper fit. FIG. 2 shows ahook-and-loop fastener (as sold under the trademark Velcro®) patch 20affixed to each side of wedge body 11 permits straps 6 havingcorresponding hook-and-loop fastener patches to be adjusted in bothlength and location. Buckles and snaps may also be used to providesimilar functionality. A strap may be a single unit that is detachableonly at one or both sides of the wedge body 11, or it may be a two-pieceunit that is fastened to each side of the wedge body 11 and joined by abuckle or other type of fastener

To provide a more secure leg fixation, the harness may also comprise agarter strap 18 that is affixed to the front of wedge body 11 and to aleg encircling strap 8 that can be secured above the user's knee asshown attached to in FIG. 1.

The upper surface 12 of wedge body 11 may include an ergonomicindentation 22 that conforms in a general way to a user's kneefront andshin. This would be a groove running from the distal end, where it isopen, either to all the way to the proximal end where it is open, or tonear the proximal end where it is closed and shaped to receive theuser's kneefront in a semi-globular hollow. Since the human leg israrely a simple cylinder, and since the shin wedge should be usable bypersons with a range of leg sizes, the groove should be a portion of anelliptical cylinder, that is, it should be wider than it is deep.

The wedge body 11 may be made of more than one piece. The upper surface12 may comprise a layer of material that is different than the bulk ofthe wedge body 11. The distal end 28 of the upper surface 12 may extendbeyond the rear face 16, in case longer support of the shin is desiredwhile adequate gripping of the inclined surface can be achieved with ashorter length of the lower surface 13.

To further improve comfort, a resilient covering 23 of plastic foam orgel may be formed onto upper surface 12, either just where the kneefrontmakes contact, as illustrated, or along the full length of the uppersurface. This feature can apply to either a flat upper surface or anupper surface that has an ergonomic indentation.

In its simplest embodiment, the lower surface 13 of wedge body 11directly contacts the inclined roof on which it is deployed. Moretypically though, a somewhat denser plastic bottom pad 24 a is affixedto the bottom of wedge body 11 to form the lower surface 13, so as toprovide better durability than the lighter material, such as expandedpolystyrene or thermoplastic elastomer, that is preferred for wedge body11. The bottom pad 24 a should have a large coefficient of friction toresist sliding. The bottom pad 24 a may have a flat, convex, or concaveshape when not in use, but when the user is kneeling the bottom pad 24 ashould conform to the surface on which the user is working in order tomaximize contact with that surface. The surface of the bottom pad 24 amay have knobs or ridges to enhance its coefficient of friction.

Bottom pad 24 a may be permanently bonded to the bottom of wedge body11. Alternatively, for added flexibility, bottom pad 24 a may be madereplaceable by providing temporary fixation means such as thehook-and-loop fastener (as sold under the trademark Velcro®) strips 25shown on replaceable pad 24 b. However, the fastening system must resistsideways motion as much as the coefficient of friction on the bottom padresists sliding down the roof, for it is pointless for the bottom pad togrip well to the roof if it does not stick well to the wedge body 11. Ifthe bottom pad is replaceable, worn pads can be replaced with new padswith the economy of retaining the wedge body 11 and its harness.

The bottom pad may have a constant thickness as shown as 24 a or elsehave varying degrees of wedge-shape such as shown by replaceable pads 24b and 24 c. If wedge-shaped, the replaceable pads would provide the userwith a means of adapting a single shin wedge 2 to work on different roofpitches.

In normal use, a user will have a pair of matching shin wedges 2, one oneach leg. There is no necessity for the shin wedges to be configureddifferently for the left and right legs, but in embodiments that haverounded edges 26, there can be a benefit from having the inside edge(that is nearer the centreline of the body) more rounded than theoutside edge. In embodiments that have a resilient covering 23 on theupper surface, that covering may optionally be shaped differently forthe left leg and right leg.

The user must be facing substantially up the slope of the roof whilewearing the shin wedges, and can easily crawl up the slope. The useralso can easily move sideways while facing up the slope, and can movedown the slope by crawling backwards. What the user cannot do is remainkneeling while facing sideways on the roof, or facing down the slope.However, the user can easily move about by standing up and walking onthe slope while still wearing the shin wedges.

If the user wants to ascend or descend by ladder, some caution isrequired, especially if he is wearing shin wedges having a large wedgeangle. The shin wedges will collide with the rungs. One reason why theshin wedges are not as long as the entire shin is to provide betterclearance from the rungs of a ladder. Also, the attachment harness inmost forms will permit the shin wedges to be swung away from the frontof the shin, and so out of the way of the ladder.

It should be understood that where this description refers to user'sshins and knees and other body parts, it envisages a person within therange of common adult sizes. Many modifications and variations besidesthose mentioned herein may be made in the techniques and structuresdescribed and depicted herein, resulting in other embodiments of thepresent invention without departing from the concept of the presentinvention. The foregoing disclosures should not be construed in anylimited sense other than the limits of the claims that follow. Thus thescope of the invention should be determined by the appended claims andtheir legal equivalents rather than by the examples given.

1. A shin wedge comprising a body that is wedge shaped, comprising anupper surface that is dimensioned and configured to supportingly receivethe user's kneefront and to supportingly receive a portion of a user'sshin, wherein said upper surface extends from a user's kneefrontdistally to more than one-quarter of the distance along said user's shinbut to less than one-half of the distance along said user's shin; alower surface comprising a substantial area that is substantially flat,wherein said lower surface intersects said upper surface at a wedgeangle, being the included angle; a third surface that faces in thedirection of a user's foot; one or more harness straps connected to saidbody, dimensioned and configured to secure the shin wedge to a user'sleg.
 2. The shin wedge of claim 1, wherein said upper surface is flat.3. The shin wedge of claim 1, wherein said upper surface is configuredwith a groove that is a portion of an elliptical cylinder running theentire length of the shin wedge.
 4. The shin wedge of claim 1, whereinsaid upper surface is configured with a groove that is a portion of anelliptical cylinder running from the distal end of the shin wedge tonear the proximal end, where said groove terminates in a semi-globularhollow configured to receive the user's kneefront.
 5. The shin wedge ofclaim 1, wherein said wedge angle is chosen to be within plus or minus10 degrees of the pitch of a roof on which its user kneels.
 6. The shinwedge of claim 1, wherein said wedge angle is chosen to be within therange 10 degrees to 40 degrees.
 7. The shin wedge of claim 1 whereinsaid lower surface comprises an external covering of material having ahigh coefficient of friction.
 8. The shin wedge of claim 7 wherein saidexternal covering comprises ridges or knobs of the same material.
 9. Theshin wedge of claim 7 wherein said external covering is detachable fromand re-attachable to the remainder of said shin wedge.
 10. The shinwedge of claim 7 wherein said external covering is wedge shaped.
 11. Theshin wedge of claim 1 wherein said upper surface comprises a resilientcovering.
 12. The shin wedge of claim 11 wherein said resilient coveringis made of plastic foam or gel.
 13. The shin wedge of claim 11 whereinsaid resilient covering is shaped for either the left leg or the rightleg of a user.
 14. The shin wedge of claim 1 wherein there are at leasttwo of said harness straps, all configured to fit a user's leg below theknee.
 15. The shin wedge of claim 1, wherein said harness strapscomprise at least one harness strap configured to fit a user's leg belowthe knee and one harness strap configured to fit the user's leg at orabove the knee.
 16. A shin wedge comprising a body that is generallywedge shaped, having an upper surface in the range 6 inches to 16inches, and having a lower surface, and having a third surface thatfaces in the direction of a user's foot; support means upon said uppersurface that is dimensioned and configured to support a portion of auser's leg; gripping means upon said lower surface that is adapted toresist sliding along a surface on which it rests; attachment means toconnect said body to a user's leg.
 17. The shin wedge of claim 16,wherein the height of said third surface establishes a dihedral anglebetween said upper surface and said lower surface that is between 10degrees and 40 degrees.
 18. The shin wedge of claim 16, wherein saidsupport means comprises a groove that is a portion of an ellipticalcylinder running from the distal end of the shin wedge to at least nearthe proximal end.
 19. The shin wedge of claim 18 wherein said groove islined with a resilient covering.
 20. The shin wedge of claim 16, whereinsaid gripping means comprises a material having a coefficient offriction that effectively prevents slipping along said surface on whichit rests, wherein said surface on which it rests is selected from thegroup consisting of asphalt shingles, wood, copper, steel, tile, slate,and waterproofing membrane.
 21. The shin wedge of claim 16, wherein saidattachment means comprises at least two straps that encircle a user'sleg and grip said user's leg.